Railroad or highway in many countries is very popular transport facility. For example, in the high-speed railroad system, the train speed typically may reach as high as 300 km/hr, and the high-speed train is usually serving for the passenger with long-distance travel. The ease of use for communications services is very attractive to passengers in the fast-moving vehicle. As the general experiences from the passengers aboard the high-speed rail or fast-moving vehicles on the road, although the speed may greatly save the travelling time, the rapid movement also causes that the passengers have difficulty to use wireless communication services on the vehicle.
In other words, in the mobile environment, the passenger in the vehicle often encounters a poor condition for wireless communication and even the case of a communication break. The frequency shift caused by Doppler Effect is very serious when in the mobile environment, particularly to the rapid movement. The coherent time is then quite small and it causes the difficulty for channel estimation and reception of the wireless radio signal. On the other hand, since the train on the rail or other vehicle on the road moves in high speed, the handover procedure is frequently performed between the communication device on the vehicle and the base stations inevitably. This further causes high packet loss probability due to the frequently performing of the handover procedure.